1. Field of the Invention
The present invention relates to a hand-held drive-in tool for driving fastening elements in a workpiece and including a housing, a guide located in the housing, a drive-in ram displaceable in the guide for driving in a fastening element, a spring for driving the drive-in ram, a tensioning device for loading the driving spring and including a motor and a threaded spindle rotatable by the motor, a locking device for retaining, in its locking position, the driving spring in its loaded position, and an actuation switch for displacing the locking device from the locking position of the locking device to a release position of the locking device in which the driving spring is displaced from its loaded position to its release position for driving the drive-in ram.
2. Description of the Prior Art
Drive-in tools of the type discussed above can be driven, e.g., electrically, with a driving spring serving as an energy accumulator for the drive-in ram. The driving spring is loaded or tensioned by a tensioning mechanism. The advantage of such drive-in tools consists in their simple and easy-to-produce construction.
A drive-in tool, which is formed as an electric nailer, is disclosed in U.S. Pat. No. 3,810,572. The disclosed drive-in tool has a drive-in ram the end of which remote with respect to a drive-in direction, is formed as a spindle-shaped threaded section. A radially outer sleeve, which surrounds the drive-in ram, is rotated by a drive motor, whereby balls, which are displaceable within the sleeve, engage the thread of the threaded section of the drive-in ram to displace the drive-in ram against the driving spring. For initiating a drive-in process, there is provided a stop sleeve that is displaceable over the outer sleeve and that is displaced axially upon actuation of a trigger in order to displace the locking balls radially outwardly in their release position. Another stop sleeve, which is displaceable over the first stop sleeve, controls the radial release of the thread-engaging balls.
The drawback of the drive-in tool, which is disclosed in U.S. Pat. No. 3,810,572, consists in a very complex arrangement of the three sleeves, which increases the costs of the drive-in tool, on one hand and, on the other hand, upon actuation of the drive-in tool, the entire force of the driving spring is applied, in a short time, to a very small surface on the edge of the thread where the last locking ball has been released. This leads to a danger of the thread edge being chipped.
A drive-in tool of the type discussed above and which is formed as an electric tacker, is disclosed in German Publication DE 32 37 087 A1. In the disclosed drive-in tool, a drive-in ram, which is formed as a striker, is driven by a rotatable motor against a driving spring in a loaded position. To this end, on the drive-in ram, there is provided toothing engageable with a threaded spindle driven by the electric motor. In its loaded position, the driving spring pivots the threaded spindle out of its engagement with the toothing on the drive-in ram. The drive-in ram is retained in the loaded position by a locking member. In order to initiate a drive-in process, an actuation switch such as an actuation lever or push-button is actuated in response to which the locking member is released from its locking position with the drive-in ram. The fastening elements which a driven-in with an electric tacker, can be stored, e.g., in a magazine.
The drawback of the drive-in tool of DE 32 37 087 consists in that a construction with a controlled, pivotal-out spindle is rather expensive. Moreover, the pivotal-out spindle is two large and expensive, which is a big drawback in hand-held drive-in tools.
Accordingly, an object of the present invention is to provide a drive-in tool of the type discussed above in which the drawbacks of the prior art drive-in tool are eliminated.